1. Field of the Invention
The present invention generally relates to displays using backlights, and more particularly to a method and an apparatus for adjusting backlight brightness that capable of reducing the time it takes to adjust backlight brightness according to the brightness of image data.
2. Description of the Related Art
Conventional display devices with backlight consist of the panel part that expresses the image and the backlight part that emits light. Since the panel cannot express the image with sufficient brightness by itself without backlight, light sources such as Cold Cathode Fluorescent Lamp (CCFL), External Electrode Fluorescent Lamp (EEFL), and Light Emitting Diode (LED) are used as backlight to display the panel image.
In general, the display device has the function of adjusting backlight brightness as bright or dark. The function is used to reduce the amount of light in a dark environment and when the backlight is too bright or to increase the amount of light in a bright environment.
A recent trend involves analyzing the image information and increasing backlight brightness if the image is bright and reducing backlight brightness if the image is dark. Such brightness adjustment method reduces unnecessary consumption of the light source and improves image quality.
For example, Korean Patent Publication No. 10-2006-0124132 discloses an LCD display device that adjusts backlight brightness to improve image quality. This LCD display device includes a timing controller that arranges the R, G, and B data signal supplied in frame units by the system and generates a fixed control signal; a data processing unit that generates a fixed amount of brightness voltage for each frame unit using the histogram obtained by analyzing the histogram for the R, G, and B data signal; a backlight controller generating a modulated brightness voltage that was increased or decreased by a fixed step by comparing the brightness voltage for each of the frames; and the backlight that adjusts and generates lights according to the brightness voltage generated by the backlight controller.
Similar to the abovementioned conventional art, the main trend involves adjusting the brightness of the entire backlights for each frame. In this organization, the brightness voltage is changed for each frame that differs by light source. If a lamp source such as CCFL is used, N 1-dimensional partitions are made, and light source brightness is changed for each section.
The reference value of an image for adjusting backlight brightness is analyzed in general with the histogram for such image. Since a histogram adequately expresses the distribution of bright and dark regions in an image, selecting the desired brightness adjustment value is only appropriate. Note, however, that analyzing an image using a histogram requires a computation process for each pixel as well as considerable time.
Therefore, if the conventional method wherein histogram computation is carried out for the entire image is used, and the computation takes a long time, a delay will occur in the display device. In this case, the production cost per unit will increase because a faster chip set needs to be used when manufacturing a chipset that realizes the function.